BBB, remember that MIDI has
no sound at all. It is just commands that must be played on either a hardware synth or a software synth. The hardware synth that is built in to most PC motherboards is really terrible, and that is what makes some people think MIDI must always sound really terrible.
A good place to listen to some examples of these is the PG Music Dare to Compare page. You will quickly realize two things: there is a huge variation in quality, and you can spend little or lots of money.
Go here:
http://www.pgmusic.com/dare-to-compare.htmFYI, I use a Roland Fantom XR, which is like a much-enhanced SD-20.